Torpedoes which are operated by a liquid fuel require the fuel tank to be pressurized to a predetermined level so as to maintain a constant flow of fuel to a propulsion motor. The fuel tank in this type of torpedo is normally a section of the torpedo wherein the confines of the tank are defined by a cylindrical hull portion of the torpedo with a pair of spaced apart plate type bulkheads at fore and aft ends thereof. In the past a carbon dioxide pressure bottle has been utilized to supply the gas necessary to maintain the fuel tank at a predetermined pressure, normally between 100 to 180 psi. With this arrangement the carbon dioxide bottle takes up space within the torpedo. Further, it has been desirable to increase the internal fuel tank pressure to between 180 to 270 psi which would require even a larger CO.sub.2 pressure bottle. While the tank could be directly open to ambient sea water this would result in unnecessarily high pressures within the tank, thus requiring significantly thicker bulkheads at each end of the tank to withstand the pressures involved.